Light valve



Nov. 2, 1943. w. D. BUCKINGHAM 2,333,517

LIGHT VALVE Filed July 12, 1941 FIG. I FIG. 2

,2' 22 AMPLIFIER AMPLIFlER INVENTOR W. D. BUCKINGHAM ATTORNEY Patented Nov. 2, 1943 LIGHT VALVE William D. Buckingham, Southampton, N.

Y., as-

signor to The Western Union Telegraph Company, New York, N. Y., a corporation of New York Application July 12, 1941, Serial No. 402,12! 2 Claims. (cure-100.4) a

This invention pertains generally to electrooptical Signaling systems and more particularly to electrically operated optical devices for use in connection with sound recording and reproducing systems. v

The common types of sound recording and re: producing systems include a variable beam of light created either by means of a source of light, the intensity of which varies in accordance with electrical current variations, or by means of a light valve which acts directly on a beam of unmodulated light under the control of variable electrical currents. These devices are commonly used in connection with microphone or loud speaker circuits for converting sound energy into permanent records on light sensitive film or for converting the recorded sound into electrical current variations in a loud speaker circuit. Difliculties have been encountered in the use of variable intensity light sources for the reason that such sources do not faithfully convert electrical variations into light variations either because of a mechanical weakness or because of inherent characteristics which make it impossible to obtain modulated light including a suflicient range of frequencies to provide faithful sound reproduction. Light valves present somewhat similar difiiculties because of electrical and mechanical limitations.

According y, the principal object of this invention is to provide a means for varying the intensity of a beam of light and eliminating the previous mechanical and electrical limitations inherent in light modulating apparatus.

A further object of this invention is to elimi-. nate the necessity of utilizing a means for directly varying the intensity of a beam of light.

Still another object of this invention is to pro= vide a device capable of creating a variable beam of light for use in sound recording and reproducing systems.

Further objects and advantages of this invention will be apparent after consideration of the following description taken in connection with the accompanying drawing, wherein:

Fig. 1 is a diagrammatic illustration of a sound recording system embodying the invention; and

Fig. 2 a diagrammatic illustration of the invention as it is embodied in a sound reproducing system.

Fig. 1 of the drawing illustrates a sound recording system comprising a microphone I which may be of any well-known form for converting sound energy into electrical energy, together with a suitable amplifier 2 connected for amplifying the electric currents which represent the aforementioned sound energy. An electromagnetic motor device 4 is connected in the output of the amplifler 2 and as shown includes a permanent magnet 5, pole pieces 6 and I, actuating coil l0 and vibratable armature II. It is not necessary that the particular form of electromagnetic motor illustrated in the drawing be used in a system of this nature, as any form of motor, such as those utilized for actuating loudspeakers or mechanical recorders, may be used in its stead.

An important feature of this invention'resides in the provision of a very small (light source [2 attached in any suitable manner to be vibrated by the armature H. Light source I2 is as light in weight as possible and preferably has a mass of, and is of the type and size utilized in, exploratory devices such as those used for investigating the interior of the human body whereby the load imposed on armature l l is negligible. The light source l2 may be energized by any suitable form of source of electrical energy [4.

The optical system includes whatever lenses are required, such as lens l6, and the light slit I! in screen 19. The light entering the slit I1 is brought to a focus on light sensitive film 20 or other recording medium and the width of slit i1 is so chosen that it equals the thickness of the lightbeam at said slit so that movement of source I: causes varying amounts of said beam to impinge on screen H! at the edge of slit I'l whereby varying amounts of light pass through it Sound energy impinging on the microphone l is converted into electrical currents or amplitudes corresponding to said sound energy which are amplified in the amplifier 2 and fed through coil ID of electromagnetic motor 4. The reaction between the flux crossing the air gap between pole pieces 6 and 1 under the influence of the permanent magnet 5 and the electromagnetic field generated by sound currents flowing in coil It causes armature H and light source 12 to vibrate back and forth in the horizontal plane of the motor 4. Thus, the beam of light emanating from source l2 and concentrated by lens I6 is increased and decreased as it vibrates and is intercepted in varying amounts at slit l1, whereby the quantity of light impinging onfilm 20 is increased and decreased in accordance with the sound energy impinging on microphone I. From the above description it is evident that light variations are recorded on film 20 without the use of a variable light source or a light valve.

Fig. 2 illustrates an electrical sound reproducingsystem embodying this invention and comprising the record 22- which may be of any suitable term so long as it includes a sound track of Phy cal proportions representing sound energy. Needle 23 is associated with record 22 in such relation that it is vibrated in accordance with the soun'd vibrations recorded on th record. Needle 23 may be supported in any suitable fashion by means of pivoted arm 24 whereby the sound track causes it to vibrate about the pivot point 26. Here again the light source I2 is supported on the end of arm 24 to be vibrated in accordance with the recorded sound. Light emanating from source I2 is concentrated into a beam by lens I6 and focused through slit II in screen l9. Here again slit Il passes v ry amounts of light, depending on the position at any moment of source l2. The light beam fails at its focus on the electrode of photoelectric cell 28 which converts the light variations into variable electric currents. These currents are amplified in ampliiier 29 and iedthrough loudspeaker 30 which.

. of intelligence is applicable to any form of system adapted to provide mechanical vibration corresponding to any type of electrical signals. For instance, this application is applicable to facsimile signaling systems wherein either information or pictures are transmitted.

Modifications oi this invention other than those illustrated herein will be readily apparent to persons of ordinary skill in the art, and therefore it is desired that this invention shall be limited only as required by the prior art and the appended claims.

, I claim:

1. In a sound recording system, a source of sound modulated electrical current, electromagnetic means connected to said source comprising a vibratory member, the mechanical vibrations of which vary in amplitude in proportion to the amplitude variations of said current, a-primary source or light vibrated by saidvibratory member, a light sensitive recording medium, an optical system for focusing light from said light source on said recording medium, and a screen havins a slit therein, said slit being dimensioned to normally pass said iocused light and to interrupt an amount of light in said beam in proportion to the amplitude of vibration thereof.

2. In a signaling system, a vibratory member, means for vibrating said member in such fashion that the mechanical vibrations therebf vary in amplitude in proportion to the vibrating force of said means, a primary source of light attached directly to and vibrated by said vibratory member, a light sensitive medium, an optical system in fixed position between said vibratory member and said medium for focusing light from said source on said medium, and a screen having a slit 'therein, said slit being dimensioned to normally pass said focused light beam and to interrupt an amount of lightin said beam in proportion to the amplitude of vibration thereof.

WILLIAM BUCKINGHAM. 

